As an emphatic form of the printer's instruction sic, this is sometimes seen, almost always misused, and in those very rare circumstances when it would be meaningful, it would probably be unrecognized anyway.
The common misuse is just as a sneering "look at that!". For example, quoting from a harmless text from any time before about 1970, containing words like "Man is the master of his environment", some people can't resist putting in a sic after the gasp! sexist language. We've all seen examples of this; it's an abuse of sic, and if it's got an exclamation mark after it, it's an abuse of the exclamation mark too. Both are all too common excesses. But they're not interesting.
The interesting thing is where you have a situation that seems to require the elevation of (1) 'sic' = "No, what you just read is correct, though it doesn't look right" to (2) 'sic!' = "No, I promise you, no matter what you think you know, this really is as intended, and the printers did not ignore the 'sic'."
The point is, use of it by itself is almost certainly self-defeating. The reader either will not know what you're talking about, or will assume the printer got it wrong or corrected your mistake, or...
READER'S VOICE: What about an example, Gritchka?
Okay, Sir Malcolm Williamson is at present* the Master of the Queen's Music (sic), meaning he is the official composer for royal occasions - the musical equivalent of Poet Laureate. Why the 'sic'? Well if you don't know what I'm referring to, it's baffling, isn't it? There's nothing strange-looking about 'Master of the Queen's Music', is there?
Well yes there is, because traditionally it's Musick with a K. If I had written that Sir Arnold Bax used to be Master of the Queen's Musick (sic), you'd have clocked the K and the 'sic' and thought, Oh isn't that quaint, it's Musick with a K. But some people already knew this.
Now consider these knowing people's reactions to the following:
- Williamson is Master of the Queen's Music
Huh, poor ignorant blighter doesn't know it's one of the quaint titles with a K on the end.
- Williamson is Master of the Queen's Music (sic)
Huh, poor sod knew it had a K on the end but has got lumbered with ignorant printers who lopped it off.
- Williamson is Master of the Queen's Music (sic!)
What are you talking about, 'sic!'? Are you stupid, or are your printers, or am I missing something!?
In fact when Williamson was appointed the title was changed to use 'Music' so spelt. And this is an ideal candidate for using sic!... if you could trust people to understand it.
Another instance I can think of is the early Jane Austen work commonly but erroneously referred to as Love and Freindship. In fact she herself corrected the title to Love and Friendship.
* At time of writing. Died 2003. The point still applies to his successor.